The present disclosure is related to a display unit of a parallax barrier type that enables a stereoscopic display, a barrier device for use in such a display unit, and a method of driving the display unit.
In recent years, display units capable of achieving a stereoscopic display have been attracting attention. The stereoscopic display displays left-eye images and right-eye images with parallax components (different perspectives) with respect to one another, allowing viewers to recognize those images as stereoscopic images with a depth by viewing each of those images with their left and right eyes. Further, display units have been also developed that enable to provide more natural stereoscopic images to viewers by displaying three or more images with parallax components with respect to each other. These display units include a display unit of a parallax barrier type. This type of a display unit displays a plurality of images (perspective images) with parallax components with respect to each other at the same time, and makes viewed images different depending on a relative positional relationship (angle) between a display unit and view points of a viewer. For example, Japanese Unexamined Patent Application Publication No. 2009-104105 discloses a parallax-barrier-type display unit using a liquid crystal device as a barrier.
Meanwhile, in a liquid crystal display (LCD) unit, for example, a VA (Vertical Alignment) mode liquid crystal has been often used. In such a liquid crystal display unit, liquid crystal molecules are aligned with a longitudinal direction thereof perpendicular to a substrate surface when no voltage is applied (in an off state), whereas the liquid crystal molecules are aligned to fall down (tilt) depending on a magnitude of a voltage when a voltage is applied (in an on state). Therefore, when a voltage is applied to a liquid crystal layer in a state where no voltage is applied, and the liquid crystal molecules that are aligned to be perpendicular to the substrate surface fall down, they fall down in any direction, which may lead to a turbulent alignment of the liquid crystal molecules. In this case, in such a liquid crystal display unit, the response to a voltage is slow.
Consequently, to control a direction where the liquid crystal molecules fall down during a voltage response time, a method of arranging the liquid crystal molecules to be tilted toward a specific direction in advance (of giving a so-called pre-tilt) has been utilized. For example, Japanese Unexamined Patent Application Publication No. 2003-279946 and No. 2006-330638 propose a PSA (Polymer Sustained Alignment) method wherein a plurality of slits are provided on pixel electrodes to hold the liquid crystal molecules in a pre-tilt state using a polymer. According to such a method utilizing a pre-tilt, it is possible to improve the voltage response characteristics of the liquid crystal molecules.